Self-balancing scooter and main frame assembly thereof

ABSTRACT

A self-balancing scooter and a main frame assembly thereof are provided. The self-balancing scooter includes a first main frame and a cooperated second main frame. The first main frame includes a first connecting portion, the first connecting portion includes a first end surface, the first end surface defines a guide hole, and the guide hole is positioned between a center and an edge of the first end surface. The second main frame includes a second connecting portion, the second connecting portion includes a second end surface corresponding to the first end surface of the first connecting portion, the second end surface defines a conduit, the conduit is positioned between a center and an edge of the second end surface, the conduit is accommodated in the guide hole, and the first connecting portion is assembled and connected to the second connecting portion.

FIELD OF THE DISCLOSURE

The disclosure relates to the field of scooter technologies, and moreparticularly to a self-balancing scooter and a main frame assemblythereof.

BACKGROUND

A self-balancing scooter, is also named as hoverboard or self-balancingboard. A working principle of the self-balancing scooter is mainly basedon a basic principle called “dynamic stability”, which uses a gyroscopeand an acceleration sensor inside a scooter body to judge a posturestate of the scooter body through a precision and high-speed centralmicroprocessor. After calculating appropriate instructions, drive amotor to achieve a balanced effect.

The self-balancing scooter usually includes two connected main frames, adriving battery, a control circuit board, two hub motors, and twowheels, etc. The two main frames are configured to form a pair ofarticulated pads on which a rider places their feet. The driving batteryis usually installed at a bottom end of one of the main frames, and thecontrol circuit board is usually installed at a bottom end of the othermain frame. The hub motors are respectively located inside the wheels,and the wheels are mounted at outer ends of the above-mentionedconnected main frames. Since an electrical connection is requiredbetween the driving battery and the control circuit board, an electricalconnection is also required between the control circuit board and thetwo hub motors, wires for performing the electrical connection need topass between the two main frames.

The two main frames are generally connected by a connecting shaft. Tofacilitate the passage of the wires, the connecting shaft is generally ahollow tube, so that the wires can pass through the through hole in theconnecting shaft. Due to a generally cylindrical shape of a main body ofthe connecting shaft, during an operation of the self-balancing scooter,with a slight swing of the main frame, the connecting shaft usuallygenerates continuous rotation. It may cause the wires located therein torotate at the same time, and it is possible to cause the wires to twisttogether and eventually break.

SUMMARY

On such basis, it is necessary to provide a self-balancing scooter and amain frame assembly thereof. The self-balancing scooter is provided witha special wire channel to facilitate the passage of the wires andprevent the wires from being damaged.

In an embodiment, the disclosure provides a self-balancing scooter. Theself-balancing scooter includes a first main frame and a cooperatedsecond main frame. The first main frame includes a first connectingportion, the first connecting portion includes a first end surface, thefirst end surface defines a guide hole, and the guide hole is positionedbetween a center and an edge of the first end surface. The second mainframe includes a second connecting portion, the second connectingportion includes a second end surface corresponding to the first endsurface of the first connecting portion, the second end surface definesa conduit, the conduit is positioned between a center and an edge of thesecond end surface, the conduit is accommodated in the guide hole, andthe first connecting portion is assembled and connected to the secondconnecting portion.

In an embodiment, the self-balancing scooter further includes aconnecting shaft, the first end surface is provided with a firstconnecting hole and the second end surface is provided with a secondconnecting hole, and the connecting shaft extends through the firstconnecting hole and the second connecting hole to connect the firstconnecting portion and the second connecting portion.

In an embodiment, each of a cross-section of the conduit at the secondconnection portion and a cross-section of the guide hole at the firstconnecting portion is an annulus, and a center of the annulus is locatedon an axis of the connecting shaft.

In an embodiment, a central angle range of two concentric arcsrespectively at left and right sides of the cross-section of the conduitat the second connecting portion is 5˜45 degrees, and another centralangle range of two concentric arcs respectively at left and right sidesof the cross-section of the guide hole at the first connecting portionis 6˜90 degrees.

In an embodiment, the first end surface of the first connecting portionfurther defines a second conduit, and the second conduit is positionedbetween the center and the edge of the first end surface; the second endsurface of the second connecting portion further defines a second guidehole, the second guide hole is positioned between the center and theedge of the second end surface; the second conduit is accommodated inthe second guide hole when the first connecting portion is assembled andconnected to the second connecting portion.

In an embodiment, a distance between the first end surface and thesecond end surface is 0.5 millimeters to 8 millimeters, when the firstconnecting portion is assembled and connected to the second connectingportion.

In an embodiment, an axis of the conduit is perpendicular to the secondend surface.

In another embodiment, a main frame assembly of a self-balancing scooteris provided. The main frame assembly includes a first main frame and acooperated second main frame. The first main frame includes a firstconnecting portion, the first connecting portion includes a first endsurface, the first end surface defines a guide hole, and the guide holeis positioned between a center and an edge of the first end surface. Thesecond main frame includes a second connecting portion, the secondconnecting portion includes a second end surface corresponding to thefirst end surface of the first connecting portion, the second endsurface defines a conduit, the conduit is positioned between a centerand an edge of the second end surface, the conduit is accommodated inthe guide hole, and the first connecting portion is assembled andconnected to the second connecting portion.

In an embodiment, the self-balancing scooter further comprises aconnecting shaft, the first end surface is provided with a firstconnecting hole and the second end surface is provided with a secondconnecting hole, and the connecting shaft extends through the firstconnecting hole and the second connecting hole to connect the firstconnecting portion and the second connecting portion.

In an embodiment, each of a cross-section of the conduit at the secondconnection portion and a cross-section of the guide hole at the firstconnecting portion is an annulus, and a center of the annulus is locatedon an axis of the connecting shaft.

In still another embodiment, a self-balancing scooter is provided. Theself-balancing scooter includes a first main frame, a second main frame,and a connecting shaft. The first main frame includes a first connectingportion, the first connecting portion includes a first end surface, afirst guide hole, and a first connecting hole, an axis of the firstguide hole and an axis of the first connecting hole are individuallyperpendicular to the first end surface, the first connecting holeextends through a central position of the first end surface. The secondmain frame includes a second connecting portion, the second connectingportion includes a second end surface, a first conduit, and a secondconnecting hole, an axis of the first conduit and an axis of the secondconnecting hole are individually perpendicular to the second endsurface, the second end surface is parallel to the first end surface,the second connecting hole extends through a central position of thesecond end surface and is aligned with the first connecting hole. Theconnecting shaft extends through the first and the second connectingholes thereby assembling and connecting the first and the second mainframes together. In such a state, a distance between the first and thesecond end surfaces is 0.5 millimeters to 8 millimeters, the firstconduit is accommodated in the first guide hole and matches the firstguide hole in such a manner that the first conduit is limited to rotate0 to 20 degrees relative to the first guide hole.

In an embodiment, the first connecting portion further defines a secondconduit, and the first guide hole and the second conduit are positionedrespectively at two opposite sides of the first connecting hole.

In an embodiment, the second connecting portion further defines a secondguiding hole, and the second conduit is accommodated in the second guidehole when the first connecting portion is assembled and connected to thesecond connecting portion.

In an embodiment, the second conduit matches the second guide hole insuch a manner that the second conduit is limited to rotate 0 to 20degrees relative to the second guide hole.

In an embodiment, a stiffener is provided on a hole wall of the firstconnecting hole.

In an embodiment, the cross-section of the first guide hole at the firstend surface comprises a first arc, a second semicircle, a third arc, anda fourth semicircle that are sequentially connected in that order.

In an embodiment, the center of the first arc coincides with the centerof the third arc, and the center is located at the axis of the firstconnecting hole.

In an embodiment, the connecting shaft comprises a screw, at least onespacer, at least one sleeve, and at least one nut.

In an embodiment, a diameter of the first connecting hole is equal tothat of the second connecting hole, and a diameter of the screw ismatched with that of the second connecting hole.

In an embodiment, the diameter of the second connecting hole is in therange of 8 millimeters to 30 millimeters.

The embodiments of the disclosure may have the following advantages.According to the above self-balancing scooter, a guide hole and aconduit are provided, and the wires can be arranged in the conduit.Therefore, the function of passing wires in the connecting shaft can beeliminated, and the connecting shaft can be designed to be solid. Assuch, with the same cross-sectional area of the connecting shaft, thestrength of the solid connecting shaft is higher, and the bearingcapacity of the entire self-balancing scooter is enhanced. In addition,by providing arc-shaped guide hole and conduit, when the two main framesare connected, they also have the effect of facilitating the wires andprotecting the wires from being damaged due to rotation of theconnecting shaft. By arranging the conduit and the guide hole, when thetwo main frames are connected, the alignment between the two main framescan be more conveniently achieved, and then the two main frames can beconnected using the connecting shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

Accompanying drawings are for providing further understanding ofembodiments of the disclosure. The drawings form a part of thedisclosure and are for illustrating the principle of the embodiments ofthe disclosure along with the literal description. Apparently, thedrawings in the description below are merely some embodiments of thedisclosure, a person skilled in the art can obtain other drawingsaccording to these drawings without creative efforts. In the figures:

FIG. 1 is a schematic structural view of a self-balancing scooterincluding two main frames connected and assembled together, according toan embodiment of the disclosure;

FIG. 2 is a schematic structural view of the two main frames of FIG. 1in separated state;

FIG. 3 is a schematic rear view of the main frame of FIG. 1;

FIG. 4 is a cross-sectional schematic view taken along arrow A-Adirection of the self-balancing scooter of FIG. 1;

FIG. 5 is a schematic view of an end surface of the main frame of FIG.1;

FIG. 6 is a cross-sectional schematic view of a connection shaft of theself-balancing scooter according to an embodiment of the disclosure; and

FIG. 7 is an exploded schematic view of the connecting shaft of theself-balancing scooter according to an embodiment of the disclosure.

DESCRIPTION OF REFERENCE NUMERALS

100—main frame, 1—connecting portion, 11—columnar body, 12—connectinghole, 13—guide hole, 14—conduit, 140—conduit hole, 15—hole wall,16—stiffener, 17—end surface, 18—wires, 2—connecting shaft, 21—screw,22—spacer, 23—sleeve, 24—nut

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The specific structural and functional details disclosed herein are onlyrepresentative and are intended for describing exemplary embodiments ofthe disclosure. However, the disclosure can be embodied in many forms ofsubstitution, and should not be interpreted as merely limited to theembodiments described herein.

In the description of the disclosure, terms such as “center”,“transverse”, “above”, “below”, “left”, “right”, “vertical”,“horizontal”, “top”, “bottom”, “inside”, “outside”, etc. for indicatingorientations or positional relationships refer to orientations orpositional relationships as shown in the drawings; the terms are for thepurpose of illustrating the disclosure and simplifying the descriptionrather than indicating or implying the device or element must have acertain orientation and be structured or operated by the certainorientation, and therefore cannot be regarded as limitation with respectto the disclosure. Moreover, terms such as “first” and “second” aremerely for the purpose of illustration and cannot be understood asindicating or implying the relative importance or implicitly indicatingthe number of the technical feature. Therefore, features defined by“first” and “second” can explicitly or implicitly include one or morethe features. In the description of the disclosure, unless otherwiseindicated, the meaning of “plural” is two or more than two. In addition,the term “comprise/includes” and any variations thereof are meant tocover a non-exclusive inclusion.

In the description of the disclosure, is should be noted that, unlessotherwise clearly stated and limited, terms “mounted”, “connected with”and “connected to” should be understood broadly, for instance, can be afixed connection, a detachable connection or an integral connection; canbe a mechanical connection, can also be an electrical connection; can bea direct connection, can also be an indirect connection by anintermediary, can be an internal communication of two elements. A personskilled in the art can understand concrete meanings of the terms in thedisclosure as per specific circumstances.

The terms used herein are only for illustrating concrete embodimentsrather than limiting the exemplary embodiments. Unless otherwiseindicated in the content, singular forms “a” and “an” also includeplural. Moreover, the terms “comprise” and/or “include” define theexistence of described features, integers, steps, operations, unitsand/or components, but do not exclude the existence or addition of oneor more other features, integers, steps, operations, units, componentsand/or combinations thereof.

The disclosure will be further described in detail with reference toaccompanying drawings and preferred embodiments as follows.

As described above, in the prior art, the two main frames of theself-balancing scooter are usually connected through a hollow tubularconnecting shaft, which both serves the purpose of mechanicallyconnecting the main frames and achieving the electrical connection. Whenthe self-balancing scooter is in operation, the connecting shaft usuallyrotates, and then the inner wires rotate simultaneously, it may causethe wires to twist together and eventually break.

To solve the above technical problem, as shown in FIG. 1 to FIG. 7, anembodiment of the disclosure provides a self-balancing scooter. Theself-balancing scooter includes two main frames 100 and a wire passagedevice. The wire passage device is disposed between the two main frames100, that is, positioned at end portions of the mainframe 100. The wirepassage device mainly includes two connecting portions 1 and aconnecting shaft 2. The self-balancing scooter in the embodiment of thedisclosure will be described in detail with reference to accompanyingdrawings as follows.

As shown in FIG. 1 and FIG. 2, the self-balancing scooter includes twomain frames 100, which has a substantially plate shape, are configuredto form a pair of articulated pads on which a rider places feet thereof.For the main frames 100, the outer ends thereof, i.e., two opposite endsof the two main frames 100 as shown in FIG. 1, each can be used toinstall a wheel (not shown). The main frames 100 each define aconnection portion 1 at an intermediate position between the two mainframes 100, to facilitate the connection and installation between thetwo main frames 100. In practical applications, a balance controldevice, a gyroscope, a control sub-board, wheels, a main board, and thelike are also mounted on the main frames 100 of the self-balancingscooter. The illustrated embodiment just shows the structure related tothe connection of the main frames, and the other structures have beenomitted. It is believed that people skilled in the art understand andare familiar with those omitted structures.

From the front schematic view of the main frame of FIG. 2, and the rearschematic view of the main frame of FIG. 3, it can be found out that theconnection portion 1 mainly includes two parts, one part is asubstantially regular structure like a columnar body 11, and the otherpart is an irregular supporting structure closely attached to thecolumnar body 11. The columnar body 11 has a cylindrical shape with acircular cross-section. In the columnar body 11, a connecting hole 12 isdefined along a direction perpendicular to the circular cross-section.The connecting hole 12 is located approximately at the center of thecolumnar body 11. The connection portion 1 further defines a hole wall15 extends from the columnar body 11 along the lengthwise direction ofthe connecting hole 12. The upper end of the hole wall 15 is providedwith a stiffener 16, and the stiffener 16 mechanically connects thecolumnar body 11 and the hole wall 15 to reinforce the strength of theconnecting portion 1 while reducing the weight of the connecting portion1.

As shown in FIG. 2, FIG. 4, and FIG. 5, a conduit 14 is disposed at theconnecting portion 1 of one of the main frames 100. Specifically, theconduit 14 is disposed on an end surface 17 of the columnar body 11, anda conduit hole 140 inside the conduit 14 extends and passes through thecolumnar body 11. Meanwhile, the other main frame 100 defines a guidehole 13 at a corresponding position. When the two mainframes 100 areassembled and connected together, the conduit 14 is located in the guidehole 13, and the conduit hole 140 of the conduit 14 extends through thecolumnar body 11. The cross-section area of the conduit hole 140 of theconduit 14 is larger than the cross-section area of a connectorinstalled at the end of the wires 18, so that the wires 18 and theconnector can be smoothly passed through the conduit hole 140 of theconduit 14, and thereby achieving the function of convenient alignment.

In the illustrated embodiment, the two main frames 100 each are providedwith the guide hole 13 and the conduit 14, and the guide hole 13 and theconduit 14 are substantially symmetrically disposed at both sides of theconnecting hole 12. When the two main frames 100 are mounted together,the conduit 14 is located in the corresponding guide hole 13, and theposition of the conduit 14 and the guide hole 13 on one main frame 100and the position of the conduit 14 and the guide hole 13 on the othermain frame 100 are symmetrical with respect to the axis of theconnecting shaft 2 described later. Of course, the number and structureof the guide hole 13 and the conduit 14 are not limited thereto. Inother embodiments, just one guide hole 13 may be disposed on one mainframe 100, and one corresponding conduit 14 is disposed on the othermain frame 100; or two guide holes 13 are provided at one main frame100, and two conduits 14 are provided at the other main frame 100. Theguide hole 13 and the conduit 14 may also be of other shapes, numbers,and positions. For example, the shape is circular, the number is three,and may be distributed around the connecting hole 12 like a triangle. Itis just necessary to satisfy that the guide hole 13 is larger than theconduit 14 and does not block the rotation of the two main frames 100within a limited rotation angle.

As shown in FIG. 4 and FIG. 5, the cross-section of the guide hole 13 inthe connecting portion 1 is substantially similar to a portion ofannulus, it is a generally regular closed graph that can be constitutedby multiple connected circular arcs. The cross-section of the conduit 14in the connecting portion 1 also is substantially similar to a portionof annulus, it is a generally regular closed graph that can be connectedby multiple circular arcs. Specifically, in the direction as shown inFIG. 4, the left and right sides of the cross-section of the conduit 14are composed of two arcs with the same center, i.e., two concentricarcs, and the upper and lower sides thereof are composed of twosemicircles. The central angle of the arc may be 5 to 45°, preferably 15to 25°, and the center of the arc is located on the axis of theconnecting hole 12.

Similarly, according to the direction shown in FIG. 4, the left andright sides of the cross-section of the guide hole 13 are composed oftwo arcs with the same center, i.e., two concentric arcs, and the upperand lower sides thereof are composed of two semicircles. The centralangle of the above two concentric arcs may be 6˜90°, preferably 28˜60°,and the center of the arcs is located on the axis of the connecting hole12. It is necessary to ensure that the central angle of the arc of thecross-section of the conduit 14 is smaller than that of the guide hole13.

From the above, it can be gotten that the center of the arc constitutedthe cross-section of the guide hole 13 is located on the axis of theconnecting hole 12, and the center of the arc constituted thecross-section of the conduit 14 is located on the axis of the connectinghole 12, and of course, the connecting hole 12 is coaxial with theconnecting shaft 2 described later. In the direction of arc, the arclength of the cross-section of the conduit 14 is smaller than that ofthe guide hole 13. With this design, when the two main frames 100 aremounted together, the twist angles of the two main frames 100 can belimited. In this embodiment, the limited twist angles of the two mainframes 100 may be limited to 20°, that is, the twist angle between thetwo main frames 100 ranges from 0 to 20°.

The above description mainly describes the specific structure of theconnecting portion 1 at the end position of the main frame 100. In thefollowing, the mechanical connection of the two main frames 100 will bedescribed.

As shown in FIG. 6 and FIG. 7, in an embodiment of the disclosure, twomain frames 100 may be connected and assembled together by theconnecting shaft 2. The connecting shaft 2 mainly includes at least onescrew 21, at least one spacer 22, at least one sleeve 23, and at leastone nut 24. The number of the at least one spacer 22 is three, thenumber of the at least one sleeve 23 is two, and both of the numbers ofthe screw 21 and the nut 24 are one.

When the main frames 100 are specifically assembled and connected, theshaft sleeve 23 and the spacer 22 are sleeved on the screw 21, passthrough the connecting holes 12 of the two main frames 100, and then thenut 24 is finally screwed on the end of the screw 21, thereby achievingthe connection of the two main frames 100.

In the embodiment, the diameter of the screw 21 is matched with thediameter of the sleeve 23, and the diameter of the sleeve 23 is matchedwith the diameter of the connecting hole 12. The screw 21 may be a solidbody or a hollow body. The diameter of the connecting hole 12 can be inthe range of 8 mm-30 mm.

In addition, referring back to FIG. 2, the end surface 17 is provided onthe connecting portion of each the main frame 100. When the two mainframes 100 are assembled and connected together, the distance betweenthe end surfaces 17 of the two connecting portions 1 is 0.5 mm to 8 mm.In addition, the conduit 14 may be disposed perpendicular to the endsurface 17, and the connecting shaft 2 extends perpendicular to the endsurface 17.

In the self-balancing scooter provided by the embodiment of thedisclosure, the guide hole 13 and the conduit 14 are disposed at the endof the main frame 100 to facilitate the wires 18 to pass through theinterior of the conduit 14. The conduit 14 and the guide hole 13 justslightly oscillate during the work of the self-balancing scooter, andwill not rotate relative to each other, thereby preventing the internalwires 18 in the conduit 14 from twisting and breaking and furtherpreventing the wires 18 from being damaged. In addition, by arrangingthe conduits 14 and the guide holes 13, when the two main frames 100 areconnected and assembled together, the alignment between the two mainframes 100 can be more conveniently performed, and then the two mainframes 100 can be easily connected using the connecting shaft 2.Finally, the arc length of the cross-section of the conduit 14 in thedirection of the arc is smaller than the arc length of the cross-sectionof the guide hole 13 in the direction of the arc, it plays the role oflimiting the twist angle of the main frame 100.

In another way, the self-balancing scooter in an embodiment of thedisclosure includes a first main frame, a second main frame, and aconnecting shaft 2. The first main frame includes a first connectingportion, the first connecting portion includes a first end surface, afirst guide hole, a second conduit, and a first connecting hole. Axes ofthe first guide hole, the second conduit and the first connecting holeare individually perpendicular to the first end surface, the firstconnecting hole extends through a central position of the first endsurface, and the first guide hole and the second conduit are bothpositioned between a center and an edge of the first end surface. Thesecond main frame includes a second connecting portion, the secondconnecting portion includes a second end surface, a first conduit, asecond guide hole, and a second connecting hole. Axes of the firstconduit, the second guide hole and the second connecting hole areindividually perpendicular to the second end surface. The first endsurface is parallel to the second end surface. The second connectinghole extends through a central position of the second end surface and isaligned with the first connecting hole. The first conduit and the secondguide hole are both positioned between a center and an edge of thesecond end surface. The connecting shaft 2 extends through the first andthe second connecting holes thereby assembling and connecting the firstand the second main frames together. In such a state, a distance betweenthe first and the second end surfaces is 0.5 millimeters to 8millimeters, the first conduit is accommodated in the first guide holeand matches the first guide hole in such a manner that the first conduitis limited to rotate 0 to 20 degrees relative to the first guide hole.The second conduit matches the second guide hole in such a manner thatthe second conduit is limited to rotate 0 to 20 degrees relative to thesecond guide hole. The cross-section of the first guide hole at thefirst end surface comprises a first arc, a second semicircle, a thirdarc, and a fourth semicircle that are sequentially connected in thatorder. The center of the first arc coincides with the center of thethird arc, and the center is located at the axis of the first connectinghole. The cross-section of the first conduit has a similar shape to thatof the first guide hole, but with a shorter arc length and a smallersemicircle.

In addition, it can be understood that the use of the connecting shaft 2can also be omitted when the mating structure between the guide hole 13and the conduit 14 has sufficiently strength.

The foregoing contents are detailed description of the disclosure inconjunction with specific preferred embodiments and concrete embodimentsof the disclosure are not limited to this description. For the personskilled in the art of the disclosure, without departing from the conceptof the disclosure, simple deductions or substitutions can be made andshould be included in the protection scope of the application.

What is claimed is:
 1. A self-balancing scooter comprising: a first mainframe, wherein the first main frame comprises a first connectingportion, the first connecting portion comprises a first end surface, thefirst end surface is formed with a guide hole and a first connectinghole, and the guide hole is positioned at a side of the first connectinghole and spaced from the first connecting hole; and a second main frame,wherein the second main frame comprises a second connecting portion, thesecond connecting portion comprises a second end surface correspondingto the first end surface of the first connecting portion, the second endsurface is formed with a conduit and a second connecting hole, theconduit is positioned at a side of the second connecting hole and spacedfrom the second connecting hole, the conduit is accommodated in theguide hole, and the first connecting portion is connected with thesecond connecting portion; a connecting shaft, extending through thefirst connecting hole and the second connecting hole to connect thefirst connecting portion and the second connecting portion; and wires,arranged in a conduit hole inside the conduit and passing through boththe conduit and the guide hole for electrical connection.
 2. Theself-balancing scooter according to claim 1, wherein each of across-section of the conduit at the second connection portion and across-section of the guide hole at the first connecting portion is anannulus, and a center of the annulus is located on an axis of theconnecting shaft.
 3. The self-balancing scooter according to claim 2,wherein a central angle range of two concentric arcs at left and rightsides respectively of the cross-section of the conduit at the secondconnecting portion is 5˜45 degrees, and another central angle range oftwo concentric arcs at left and right sides respectively of thecross-section of the guide hole at the first connecting portion is 6˜90degrees.
 4. The self-balancing scooter according to claim 1, wherein thefirst end surface of the first connecting portion further is formed witha second conduit, and the second conduit is positioned at another sideof the first connecting hole opposite to the guide hole; the second endsurface of the second connecting portion further is formed with a secondguide hole, the second guide hole is positioned at another side of thesecond connecting hole opposite to the conduit; and the second conduitis accommodated in the second guide hole.
 5. The self-balancing scooteraccording to claim 1, wherein a distance between the first end surfaceand the second end surface is 0.5 millimeters to 8 millimeters when thefirst connecting portion is connected with the second connectingportion.
 6. The self-balancing scooter according to claim 1, wherein anaxis of the conduit is perpendicular to the second end surface.
 7. Theself-balancing scooter according to claim 1, wherein the conduit matchesthe guide hole in such a manner that the conduit is limited to rotate 0to 20 degrees relative to the guide hole.
 8. The self-balancing scooteraccording to claim 1, wherein a stiffener is provided on a hole wall ofthe first connecting hole.
 9. The self-balancing scooter according toclaim 1, wherein a cross-section of the guide hole at the first endsurface comprises a first arc, a second semicircle, a third arc, and afourth semicircle that are sequentially connected in that order.
 10. Theself-balancing scooter according to claim 9, wherein a center of thefirst arc coincides with a center of the third arc, and the center ofthe first arc is located at an axis of the first connecting hole. 11.The self-balancing scooter according to claim 1, wherein the connectingshaft comprises a screw, at least one spacer, at least one sleeve, andat least one nut; a diameter of the first connecting hole is equal tothat of the second connecting hole, and a diameter of the screw ismatched with that of the second connecting hole.
 12. The self-balancingscooter according to claim 11, wherein the diameter of the secondconnecting hole is in the range of 8 millimeters to 30 millimeters. 13.The self-balancing scooter according to claim 1, wherein a central anglerange of two concentric arcs at left and right sides of a cross-sectionof the conduit at the second connecting portion is smaller than anothercentral angle range of two concentric arcs at left and right sides of across-section of the guide hole at the first connecting portion, arclengths of the two concentric arcs at the left and right sides of thecross-section of the conduit are respectively smaller than correspondingones of arc lengths of the two concentric arcs at the left and rightsides of the cross-section of the guide hole and thereby a twist anglebetween the first main frame and the second main frame is limited.